| |
NIS provides a simple network lookup service consisting of databases
and processes. The databases are stored at the machine that runs an NIS
server process. The programmatic interface to NIS is described in ypclnt(3NSL).
Administrative tools are described in ypinit(1M), ypwhich(1),
and ypset(1M). Tools to see the contents
of NIS maps are described in ypcat(1),
and ypmatch(1).
ypbind is a daemon process that is activated at
system startup time from the startup script /etc/init.d/rpc.
By default, it is invoked as ypbind -broadcast. ypbind runs on all client machines that are
set up to use NIS. See sysidtool(1M).
The function of ypbind is to remember information that
lets all NIS client processes on a node communicate with
some NIS server process. ypbind must
run on every machine which has NIS client processes.
The NIS server may or may not be running on the same
node, but must be running somewhere on the network. If the NIS server is a NIS+ server in NIS
(YP) compatibility mode, see the NOTES section of the ypfiles(4)man
page for more information.
The information ypbind remembers is called a binding -- the association of a domain name with a NIS server. The process of binding is driven by client requests.
As a request for an unbound domain comes in, if started with the -broadcast option, the ypbind process broadcasts
on the net trying to find an NIS server, either a ypserv process serving the domain or an rpc.nisd
process in "YP-compatibility mode" serving NIS+ directory
with name the same as (case sensitive) the domain in the client request.
Since the binding is established by broadcasting, there must be at least
one NIS server on the net. If started without the -broadcast option, ypbind process steps through
the list of NIS servers that was created by ypinit -c for the requested domain. There must
be an NIS server process on at least one of the hosts
in the NIS servers file. All the hosts in the NIS servers file must be listed in either the /etc/hosts or /etc/inet/ipnodes files along with their IP addresses. Once a domain is bound by ypbind,
that same binding is given to every client process on the node. The ypbind process on the local node or a remote node may be queried
for the binding of a particular domain by using the ypwhich(1) command.
If ypbind is unable to speak to the NIS server process it is bound to, it marks the domain as unbound,
tells the client process that the domain is unbound, and tries to bind the
domain once again. Requests received for an unbound domain will wait until
the requested domain is bound. In general, a bound domain is marked as unbound
when the node running the NIS server crashes or gets
overloaded. In such a case, ypbind will try to bind to
another NIS server using the process described above.ypbind also accepts requests to set its binding for a particular
domain. The request is usually generated by the ypset(1M)
command. In order for ypset to work, ypbind must have been invoked with flags -ypset or -ypsetme.
|
